Master cylinder for hydraulic brakes



May 30, 1939. 1.. E. LA BRIE MASTER CYLINDER FOR mmmumc' BRAKES Filed Spt. 9, 1955 s Sheets-Sheet 1- a a w BY *Q W ATTOR EY.

May 30, 1939. L. E. LA BRlE MASTER CYLINDER FOR HYDRAULIC BRAKES Filed Sept. 9, 1955 3 Sheets-Sheet 2 V20 y //4 INVENTOR.

' ATTORNE y 30, 1939- L. E. LA BRIE 2,160,075

MASTER CYLINDER FOR HYDRAULIC BRAKES Filed Sept. 9, 1955 s Sheets-Sheet s M Q 6 Q INVENTOR. woes/z .6. M5011? By W AT RNEY Patented May 30, 1939 PATENT OFFICE MASTER CYLINDER FOR HYDRAULIC BRAKES Ludger E. La Brie, South Bend, Ind., assignor to Bendix Products Corporation, South Bend, Ind., a corporation of Indiana Application September 9, 1935, Serial No. 39,735

4 Claims. (c1. 60-545) This invention relates to hydraulic control systems, and more particularly to the construction and arrangement of master cylinders for use in such control systems, and particularlyadapted for use in automotive vehicle hydraulic brake systems.

The present invention is particularly directed to a hydraulic brake master cylinder having special means associated therewith for preventing the possible occurrence of vacuum conditions in the brake system upon the return or suction stroke of the master cylinder, by permitting theeasy inflow of fluid from the reservoir 111150 the master cylinder through some form or arrangement of check valve.

Accordingly, an object of the invention is to provide a master cylinder for use in hydraulic control systems having means associated therewith for preventing the occurrence of sub-atmosgo pheric pressures in the system on the 'suctio stroke.

Another object of the invention is to provide in a master cylinder, a direct connection to the reservoir so that on return or suction stroke of 25 the master cylinderany tendency to produce a vacuum in the system will be satisfied bythe direct and prompt inflow of fluid from the reservoir. I

A further object of the invention is to provide 30 in a hydraulic brake system a master cylinder having a direct connection to a reservoir with a check valve interposed therein so as to interrupt such connection on the compression stroke.

A stillfurther object of the invention is to 35 provide a hydraulic brake master cylinder of the above type which shall be of simple construction; rugged in operation and economical to manufacture.

The above and other objects and novel fea- 40 tures of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with the accompanying drawings illustrating various modified forms of the invention. It is expressly under- 45 stood, however, that the drawings are employed for purposes of illustration pnly and are not designedas a definition upon the limits of the invention, reference being had for this purpose to the appended claims.

50 In the drawings wherein similar reference char-- acters indicate similar parts throughout the several views:

Fig. 1 is a longitudinal section through one form of the invention showing the master cylinder, reservoir and parts associated therewith;

Fig. 2 is a longitudinal section of a slightly modified form of a master cylinder showing the invention;

Fig. 3 is a longitudinal section of a master cylinder modified from that of Fig. 1 and having an 5 operating lever fulcrumed on the casing;

Fig. 4 is a longitudinal section of a master cylinder modified somewhat over that of Fig. 3;

Fig. 5 is a longitudinal section through a form of master cylinder embodying the invention but 10 adapted to be connected to a separate reservoir, and

Fig. 6 is a longitudinal section of a modified form of the type illustrated in Fig. 5.

Referring to the drawings and more particul larly Fig. 1, there is illustrated a master cylinder casing l0 having a reservoir l2, master cylinder bore l4 located thereunder, and a check valve chamber l6 having ports l8 and leading to the reservoir and cylinder respectively. 20

The cylinder bore is provided with a piston 22 having a forward knob bumper 24 about which is positioned an annular cup washer 26, the knob forming a means for limiting the forward stroke of the piston. The piston is also provided with 25 annular oil grooves 28 and an annular washer 30 set in an annular groove near the back of the piston.- The normal position or return movement of the piston is limited by an annular disc 32 set in an enlarged groove 34 in the back of 30 the cylinder. A locking ring 34 holds the annular disc in place and'in addition retains an annular cup-shaped member 36 which is adapted to carry one end of a return spring 38. A piston rod 40 is swivelly connected to the piston as at 42 and is provided at its outer end with a threaded collar ,44. The aforementioned spring 38 is positioned around the rod and is compressed between the annular cup member 36 and the collar.44. A flexible boot 46 is'secured in an annu- 4U lar groove 48 on the outside wall of the cylinder casing and also in an annular groove 50 in the threaded collar and prevents the entrance of dirt and foreign matter into the back end of the cylinder. A compensating port 52 is provided between the reservoir lland cylinder bore I 4 just forward of the return stroke position of the annular cup'washer 26.

The check valve chamber l6 which consists of a cylindrical bore with a conical inner end 54150 is arranged at one end of the cylinder and the apex of the conical bore 54 isconnected to the reservoir l2 by means of the passage It. The cylindrical'portion of the chamber is connected to thecylinder bore through a port 20. Adapted s5 to seat upon theconical surface 64 is a check valve 66 which comprises a stem member 66 having a head 60 and an annular reduced portion 62 in the stem adjacent the head. A conical washer 64 is threaded on the stem and seated on the annular reduced portion 62 and against the head 60. The valve stem is guided in a central bore 66 located in a screw plug 66 adapted to be threaded into the cylindrical chamber, and the valve stem 66 is fluted as at 10 to permit passage of fluid through the central bore 66 and to a discharge conduit, not shown, which may be fltted into'the threaded recess 12 and the end of the plug 66.

The central bore 66 may be restricted more or less as shown at 14 so that, upon the return stroke of the piston, liquid may preferably be drawn from the reservoir through the check valve rather than from the discharge conduit, thereby preventing sub-atmospheric pressure from being developed in the discharge conduit. A light spring 16 which is threaded on the valve stem 66 is adapted to hold the check valve normally on its seat. An electric stop-light swtch 16 is shown in communication with the cylinder bore so that pressures developed therein during braking may be used to operate a. suitable electric signal.

The top of the reservoir I2 is provided with a screw filler plug 60 having breathing ports 62 and an apertured baffle 64 located adjacent thereto to prevent splashing of the liquid through the port 62. The plug shown may be made from formable sheet metal and the bane 64 may be held in place in an annular pocket 66 provided during the forming process.

The modified form of the invention shown in Fig. 2 comprises a master cylinder casing I I having a reservoir I I2, master cylinder bore I I4, and check valve chamber II6, the latter being connected to the reservoir and bore by ports I I6 and I20 respectively.

A piston I22 having a forward annular cup washer I26 and bumper I24 is reciprocably mounted in the cylinder bore H4, and its return stroke position is determined by a washer I32 outwardly flanged along its inner edge as at I33, the washer being seated in an enlarged recess in the back of the cylinder and locked in place by a ring I64. A piston rod I40 swivelly secured to the piston is provided having an adjustable shouldered collar I44, carrying one end of a flexible boot I46, the other end of which is secured to the outside wall of the end of the cylinder. Around the piston rod is a return spring I66 compressed between the washer I62 and the collar I44, the spring being centered on the flange I66 of the washer.

The check valve chamber, as in Fig. 1, comprises a cylindrical bore I60 connected through port I20 to the cylinder, and a conical end I62, the apex of the conical surface being connected through port I I6 to the reservoir. A conical valve comprising a fluted stem I10 slidably mounted in the port 6 for guiding is provided with a head I12 adapted to carry aconical washer I14. An end plug I16 threaded into the valve chamber is provided with a discharge port I16, and carries on its forward face a boss I60 for receiving and centering a light spring I62 bearing against the valve washer I14.

The reservoir is provided with a compensating port I62 leading to the cylinder bore just forward of the return stroke position of the cup washer I26. Also the reservoir is provided with a filler part of the valvecap I60, and a seal I64 for a core hole preferably provided during casting.

The modifications of Figs. 3 and 4 are greatly similar to those of Figs. 1 and 2 respectively with the exception that the flexible boot employed in Fig. 1 and for preventing entrance of dirt and dust has been dispensed with in lieu of a washer type construction more suitable for use in connec tion with the fulcrumed lever shown.

In Fig. 3 for example, the cylinder reservoir and check valve construction is the same as Fig. 1, except that the cylinder casing carries a fulcrum 60 on one side thereof in which is carried a lever 62 the lower end of which is secured to the piston rod 64. The upper end of the lever 62 is provided with a series of holes 66 particularly adapted for adjustment. To prevent entrance of dirt and foreign matter, the open end of 'the cylinder is provided with an annular groove 66 carrying a washer 66 and annularly flanged packing carrying member I00, the same being held in place by a lock ring IOI. Located between the washer 66 and member I00 is an annular packing material I02 adapted to snugly but 'slidably embrace the piston rod 64. A similar arrangement is illustrated in Fig. 4, however the structure of Fig. 4 aside from the lever and cylinder end structure conforms to that of Fig. 2.

Referring to the modified forms of the invention illustrated in Figs. and 6, master cylinders of the type adapted for positioning remote from the reservoir are shown. In Fig. 5, the casing 2I0 comprises a cylinder bore 2I4 and check valve chamber 2I6 located thereabove. The cylinder bore 2I4 contains therein a piston 222 having an annular cup washer 226 carried on a central knob 224 on the forward end of the piston. The piston is also provided with a rear washer 230 and a return stroke limiting means comprising an annular disc 234 set in an annular recess 236 in the mouth of the cylinder bore, and locked in place by a ring 266; The piston also has a piston rod 24.0 swivelly secured thereo, the rod having an adjustable collar 244, carrying a flexible boot 246 secured thereto and the exterior of the rear end of the cylinder.

The check valve chamber comprises a cylindrical bore 260 terminating in a conical valve seat 262, the apex of which is connected to the cylinder bore by a compensating port 263, just forward of the release position of the piston washer 226. The cylindrical bore portion of the chamber is provided with a port 220 extending to the inner end of the cylinder. A conical check valve 210 having a downwardly-extending stem 21 guidably carried in an enlarged portion 266 of the compensating port 266 is held on its seat by a light spring 212 centered around the upper end of the valve stem and in a recess 214 formed on the under inner surface of the plug 216 threaded in the cylindrical portion of the valve chamber. The spring may be seated on a conical perforated guide stamping 266 forming a guide against collapsing of the spring and also forming a bumper limiting the movement of the check valve.

Connection to any suitable reservoir is made to a bore 260 extending into the enlarged portion 266 of the compensating port, and the cylinder discharge or motor cylinder line is connected to the central bore 264 of the plug 216.

In the modification of the invention disclosed in Fig. 6, the check valve chamber is illustrated as formed in the end of the cylinder bore. The cylinder casing 6I0 is provided with the cylinder bore 6, the same being closed atone end by a cal arrangements and forms.

plug 3l5 having a discharge port 3" therein. Adjacent the discharge end of the cylinder bore is an intersecting vertical bore 3l2 forming a check valve chamber. The upper end of this bore, above the wall of the cylinder bore 314, is provided with a conical valve seat 3l9 the apex of which is connected by ports 320 and 32l to a connection 32 adapted to lead to a fluid reservoir. The lower end of the bore emerges from the easing and is provided with a screw plug 350 upon which is carried a shouldered inwardly-extending stud 352 adapted to carry a spring 354 urged against a conical valve 356 arranged for engagement with the conical valve. seat 3). The valve is provided with a fluted stem 32I adapted to extend upwardly into the port 320 and be slidably guided thereby.

The remainder of the cylinder comprises the usual master piston 322 with a cup washer 326 carried on its forward end, the same being snapped over a shoulder pin 323. The forward face of the piston 322 is provided with an eccentric keyhole slot 330 adapted to receive a second shoulder on the pin 328, which shoulder when seated in the slot and positioned concentric is firmly held in place.

The rear of the piston is provided with the usual piston rod 340, stop washer 342 and lock ring 344 together with a flexible boot 346 attached to a collar 34"! on the rod 340 and cylinder casing. The collar 34! may be adjustably positioned on the rod so as to abut the stop washer 342 and thus limit the forward stroke of the piston. The ports 320, 32l and 324 leading to the reservoir are also connected by a compensating port 323 to the interior of the cylinder bore at'a point just forward of the return position of the piston.

The operation of the various forms of the invention will appear from the foregoing description, it being obvious that upon a forward stroke of the master piston fluid is ejected through the discharge port to the motor or wheel cylinders. Upon return stroke the check valve opens to supply fluid directly from the reservoir to offset any deficiency which might result in vacuum conditions in the line. The fluid thus temporarily borrowed from the reservoir is subsequently returned to the reservoir as fast as the wheel or motor cylinders by their return springs are able to force fluid back to the master cylinder. Thus a pressure condition is maintained in the line at all times obviating any chance of drawing air into the line as a result of vacuum conditions.

Although several embodiments of the invention have been illustrated and described, it is to be understood that the invention is not limited thereto but may be embodied'in other mechani- For example, the various features of any one of the modifications might be substituted for those of the other modifications. As such and other changes in construction and arrangement may be made'without departing from the spirit of the invention as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.

What is. claimed is:

l. A hydraulic brake master cylinder comprising a casing having a reservoir in the top thereof and a cylinder bore therebelow, and a valve chamber of cylindrical shape with a conical upper end diagonally arranged beneath said reservoir and beyond the end 'of said cylinder bore, said valve chamber having a port from the conical end of the chamber to said reservoir and having a second port by which it is connected to the cylinder bore, a plug threaded into said chamber having a central discharge port, and a valve adapted to seat on'said conical end and having a fluted stem slidable in said discharge port.

2. A hydraulic brake master cylinder comprising a casing having a reservoir on the top thereof and a cylinder bore therebelow; and a valve chamber of cylindrical shape with a conical upper end diagonally arranged beneath said cylinder and beyond the end of said cylinder bore, said valve chamber having a port from the conical end of the chamber to said reservoir and having a second port by which it is connected to the cylinder bore, a plug threaded into said chamber having a central discharge Port, a valve adapted to seat on said conical end and having a fluted stem slidable in said discharge port, and a spring interposed between said valve and said plug.

3. A hydraulic brake master cylinder comprising a casing having a reservoir on the top thereof and a cylinder bore therebelow, and a valve chamber of cylindrical shape with a conical upper end diagonally arranged beneath said cylinder and beyond the end of said cylinder bore, said valve chamber having a port from the conical end of the chamber to said reservoir and having a second port by which it is connected to the cylinder bore, a plug threaded into said chamber having a central discharge port, a valve adapted to seat on said conical end, and a spring interposed between said valve and said plug.

4. A hydraulic brake master cylinder comprising a casing having a reservoir on the top thereof and a cylinder bore therebelow, and a valve chamber of cylindrical shape with a conical upper end diagonally arranged beneath said cylinder and beyond the end of said cylinder bore, said valve chamber having a port from the conical end of the chamber to said reservoir and having a second port by which it is connected to the cylinder bore, a plug threaded into said chamber having a central discharge port, and a valve adapted to seat on said conical end.

LUDGER E. LA BRIE. 

